The purpose of this contract is to study the long-term effects of different treatment modalities for children with attention deficit hyperactivity disorder (ADHD) through a systematic follow-up of the subjects who participated in the Multimodal Treatment Study of Children with ADHD (MTA). The initial design and planning phase of the MTA study occurred during the latter portion of 1992 thru the end of 1993, where the divergent study designs and goals of the various investigators were blended into a cohesive, coherent, and scientifically rigorous final design. The 24-month MTA Study (14 months of treatment, followed by a 10-month follow-up assessment) of 579 children with ADHD was conducted at seven treatment sites over the course of the next four years. Participants were assessed before, during, and at the end of 14 months of treatment, and 10 months later. Treatment was received depending on to which one of four groups participants were randomized (medication alone, behavioral treatment alone, medication plus behavioral treatment, community treatment as usual). This five-year period was supported by NIMH cooperative agreement grants to the clinical sites. At the 24-month point, a Local Normative Control Group of grade- and school-matched non-patients was added as a comparator group. With the support of a subsequent competing supplement to each site, 36-month follow-up assessments were completed. The original MTA aims addressed the following questions: What are the differences in effectiveness for medication management versus intensive behavioral treatments? What are the additive/synergistic effects of combined medication and psychosocial treatment compared to either treatment delivered alone? What is the relative effectiveness of systematic, well-delivered treatments vs. [unreadable]standard[unreadable] treatments typically received in the community? Additional questions the MTA investigators sought to address included the prediction and mediation of treatment-related gains from individual (e.g., co-morbidity), familial (e.g., child-rearing practices), and/or social (e.g., SES) variables. This current contract supports assessment and data collection for follow-up year 12 of the MTA study, at the seven original sites. Each site is supported by an individual contract to that site.